1. Field of the Invention
This invention relates to web and sheet handling devices and more particularly to devices for selectively streaming and merging side-by-side sheets in a stream.
2. Background Information
In high-volume electronic printing applications it is often desirable to produce side-by-side images on a wide continuous web. In this manner, each printing operation by, for example, a rotating image transfer drum, produces two pages rather than one. The side-by-side images on the wide web can be the same, representing two copies of the same job; can be consecutive pages in the same job; or can be different jobs or sections of a job. At some time during the printing process, a downstream cutter and slitter forms each image into a separate page. Where the images represent consecutive pages in the same job, a merger places the images over each other. Conversely, where the images represent different jobs or separated sections, the cut and slit sheets are carried downstream in separate streams to a stacker or other post-production device. It is common for sheets to be cut after two or more ribbons of web are slit and merged over each other, in the form of a slit and merged web. In this manner, two or more overlapping sheets are cut from the corresponding merged ribbons. The slit and merge technique has limitations in speed, setup and functional versatility. The resulting output sheets must often be handled according to a very specific arrangement, and existing devices do not accommodate many different orientations or sizes.
Accordingly, it is an object of this invention to provide a versatile sheet handling device that enables selective feeding of either merged or side-by-side streams of sheets from an upstream source to a downstream post-processing device, such as a stacker. The merge and stream-handling device should operate at reasonably high speed and accommodate a variety of lengths and sizes of sheets with a high degree of accuracy in registration in both a side-by-side and upstream-to-downstream direction. The device should also enable selective offset of sheets in either a streaming or merged arrangement.
This invention overcomes the disadvantages of the prior art by providing a device for selectively merging or streaming side-by-side fed sheets using an upper and lower feed surface each of which includes an edge guide on an opposing side-by-side edge. Each of the feed surfaces can be moved in a widthwise (side-by-side) direction with respect to the other to thereby relocate its associated edge guide. As sheets pass over each of the upper and lower feed surface, a set of vacuum drive belts bias fed sheets against the respective edge guide. As respective edge guide. By selectively aligning the edge guides, and directing the sheets to either of the upper or lower feed surfaces, the sheets can be selectively aligned over each other for merged output or maintained in a side-by-side relationship or they do not overlap. A diverter assembly having a pair of side-by-side diverter halves is located adjacent to and input surface. The diverter halves can be moved separately to direct each of side-by-side slit sheets to either of the upper or lower feed surface. An output ramp assembly directs sheets from each of the upper and lower feed surfaces back onto a single feed surface for delivery to a post-production device. At this location, the sheets are delivered into two side-by-side streams, or overlying each other in a merged arrangement. Each feed surface is wide enough so that at an appropriate widthwise position. It can receive sheets from either of the two side-by-side input diverter halves. This enables the sheets to be selectively maintained in side-by-side streams, or to be passed crosswise into overlapping (merged) positions.
According to preferred embodiment the edge guide of each of the upper and lower feed surface includes actuators to move it in a widthwise direction so as to enable offset of selected sheets passing there over. In addition, an upstream cutter and slitter can be located adjacent to the input feed surface to create side-by-side cut sheets from a continuous web. The input feed surface can include a set of vacuum belts that are angled outwardly from each other in a downstream direction to provide a separation between slit sheets before they enter the diverter assembly. At least one of the feed surfaces can include a removable stream plate that covers a plurality of angled feed belts on the feed surface when sheets are driven in a side-by-side stream relationship so that excessive angular force is not applied to the streamed sheets. Finally, each of the input, upper and lower feed surfaces can be mounted on a box structure having fans mounted thereon for driving air flow through ports around respective vacuum belts to maintain frictional adhesion of sheets against the vacuum belts, while allowing widthwise translation against respective edge guides. The upper and lower feed surfaces can also include a removable cover that maintains the sheets in close proximity to the belts as they pass along the respective feed surface.